Acute myeloid leukemia (AML) is characterized by arrest of differentiation in the myeloid lineage and an over proliferation of blast cells. It is th most common type of leukemia in the United States and is primarily a disease of the elderly. Compared with their younger counterparts, elderly AML patients (age e 65 years) have worse outcome, with a median survival far less than one year. The poorer survival in the elderly has been attributed to less effective therapy, more comorbidities, and other patient characteristics. Although intensive chemotherapy is a standard treatment for younger AML patients, whether intensive or low-intensive chemotherapy will benefit elderly AML patients is not established. To date, most studies evaluating the effects of chemotherapy in elderly AML patients have been limited to small patient series from one or few clinical institutions. Medicare expenditure for elderly AML patients has steadily increased over recent years. The cost for elderly AML patients who received chemotherapy was almost three times higher than those who did not. However, there is no existing study comparing the cost-effectiveness of intensive chemotherapy versus low- intensive chemotherapy for the treatment of elderly AML patients. In the proposed study, we will assemble a cohort of approximately 5,000 elderly AML patients who were diagnosed in the Surveillance, Epidemiology and End Results program area during 2005-2009 and follow the medical care they received through the end of 2010. We will evaluate the comparative effectiveness of intensive and low-intensive chemotherapy for the treatment of elderly AML patients in two aspects, i.e., the clinical effectiveness and the cost-effectiveness. The clinical effectiveness of intensive and low-intensive treatment will be measured by 8-week and 1-year survival, and the cost-effectiveness will be measured by the length of survival, quality adjusted survival, and incremental cost-effectiveness ratio. Given the aging of the population and the continuous rise in Medicare expenditure, findings from the proposed study will not only provide valuable information for physicians and patients to choose treatment options, but also have significant health policy implications.